The present invention relates to a fishing reel having a seal mechanism for sealing a supporting structure which rotatably supports a rotating member.
Typical fishing reels are configured to wind up a fishing line on a spool via a power transmission mechanism by virtue of a rotating operation of a handle. Such power transmission mechanisms tend to be provided with a driving shaft configured to rotate in response to a rotation of a handle. A typical driving shaft is rotatably supported on a reel body via ball bearings.
Conventional reel bodies are susceptible to unwanted adhesion of foreign objects such as seawater or sand when they are used at a fishing site. Those foreign objects penetrate inside a reel body through gaps of the body and adhere to the ball bearings supporting the driving shaft, which causes the ball bearings to corrode and also degrades the rotation performance of the ball bearings.
In order to address the aforementioned deficiencies, it is common to attach elastic seal members onto the outer surface of the driving shaft in proximity to the ball bearings to make the ball bearings both waterproof and dustproof. However, the contact pressure from such elastic seal members onto the driving shaft causes the rotation performance of the driving shaft to degrade.
There is known a structure designed to ensure waterproof and dustproof capability of the ball bearing without degrading the rotation performance of the driving shaft. For example, Japanese Patent Application Publication 2003-319742 discloses a magnetic seal mechanism for sealing a reel body by retaining magnetic fluid between a magnetic holdings ring forming a magnetic circuit and a spool shaft (driving shaft).
However, the above-mentioned magnetic seal mechanism is configured to include a magnet which is sandwiched between a pair of polar plates. That configuration requires two plates for a single magnet, thus resulting in increased number of components and resulting poorer production efficiency due to more complicated assembly process. In addition, it is difficult to make the reel body compact since the body needs to have a large size of installation space corresponding to the sum of the thickness of the magnet and the pair of the plates at least at one end of the bearing. Moreover, the specific weight of the plates is as high as that of iron because the plates are made of a magnetic material, which causes greater total weight of the magnetic seal mechanism.
In addition, the afore-mentioned magnetic seal mechanism is configured such that the magnetic fluid is in direct contact with the rotating member of the driving shaft, which requires the rotating member to be made of a magnetic material. Accordingly, there are limited numbers of available options in selecting the material of the rotating member that can satisfy the desired quality requirement. Furthermore, the resulting rotating member made of a magnetic material leads to a greater weight of the entire reel.
The above-described magnetic seal mechanism may apply not only to the driving shaft rotatable in response to a rotation of a handle but also to various portions of a bearing supporting member disposed on the reel. For example, the magnetic seal mechanism may be applied to bearing portions which conventionally do not employ such a magnetic seal mechanism, such as a bearing for rotatably supporting a line roller configured to guide a fishing line to a spool. However, in case that the magnetic seal mechanism is applied to the bearing configured to support a line roller, a high-speed rotation of the rotor exerts a large centrifugal force on the line roller and its bearing and the centrifugal force causes the magnetic fluid of the magnetic seal mechanism to fly off. Although a stronger magnetic force may prevent the fly-off of the magnetic fluid, it would become necessary to increase the size of the magnet to achieve such a stronger magnetic force. Such an increased size of the magnet inevitably results in a larger size and a greater weight of the entire reel and also causes ill-balanced rotation of the rotor.